As is described further in the background discussion below, it is difficult to provide information indicating operative condition, status, and the like of a variable shutter or lens that is used to protect the eyes of a person if that lens or shutter is located in close proximity to the eyes. Because of the close proximity of the lens or shutter, it is difficult, if not impossible, accurately or conveniently to focus the eyes on status indicators or the like that are proximate the shutter or lens. Examples of such a shutter or lens include an auto-darkening welding lens used in a welding helmet, a similar auto-darkening lens used in a respirator system that employs a helmet or other face covering, etc. Exemplary information that may be conveyed to the person wearing the helmet, respirator, etc., may be shade number, sensitivity, power level, power or battery reserve, etc.
In the description herein reference will be made to a lens (also sometimes referred to as “welding lens,” “welding filter,” “shutter,” and the like), and to an automatically darkening lens (sometimes referred to as auto-darkening lens) that is able to operate automatically to control the transmission of light through the lens. The lens may be a light shutter type of a device that is able to control light transmission without distorting, or at least with relatively minimal distortion of, the light and the image characteristics carried by the light or represented by the light. Therefore, when a person looks through the lens, the image seen would be substantially the same as the image seen without the lens, except that the intensity of the light transmitted through the lens may be altered depending on the operative state of the lens. The lens may be used in a welding helmet, and the lens may be used in other types of devices, such as goggles, spectacles, face masks, e.g., for industry (such as in an industrial plant or to protect outdoor or indoor electrical workers), for dentistry to protect the fact of a dentist in the operative, respirator systems, nuclear flash eye protection devices, and other types of helmets and other eye-protection devices, etc. Such devices usually are employed to protect the face or the eyes of a person, as is known, for example, in the field of welding as well as other fields. Further, the lenses may be used in various other places to protect workers from bright light that could present a risk of injury.
For the purposes of providing eye protection, usually a welding lens provides light blocking characteristics in the visible, infrared and ultraviolet wavelength ranges. The actual ranges may be determined by the components of the lens, the arrangement of those components, and so forth. One example of such a welding lens is described in U.S. Pat. No. 5,519,522. The lens assembly disclosed in that patent includes several liquid crystal cell light shutters, several plane polarizers, and a reflector or band pass filter, that are able to reflect ultraviolet and infrared electromagnetic energy and possibly also some electromagnetic energy in the visible wavelength range. The several liquid crystal cells, for example, may be birefringent liquid crystal cells sometimes referred to as surface mode liquid crystal cells or pi-cells.
As will be described further below, the present invention may be embodied in a variable optical transmission controlling device. Such a device is described in detail with respect to use in a welding helmet. However, it will be appreciated that such a device may be employed in other environments and in other devices and systems for controlling transmission of electromagnetic energy broadly, and, in particular, for controlling optical transmission. As used herein with respect to one example, optical transmission means transmission of light, i.e., electromagnetic energy that is in the visible spectrum and that also may include ultraviolet and infrared ranges. The features, concepts, and principles of the invention also may be used in connection with electromagnetic energy in other spectral ranges.
Examples of liquid crystal cells, lenses using them and drive circuits are described in U.S. Pat. Nos. 5,208,688, 5,252,817, 5,248,880, 5,347,383, and 5,074,647. In U.S. Pat. No. 5,074,647, several different types of variable polarizer liquid crystal devices are disclosed. Twisted nematic liquid crystal cells used in an automatic shutter for welding helmets are disclosed in U.S. Pat. Nos. 4,039,254 and Re. 29,684. Exemplary birefringent liquid crystal cells useful as light shutters in the present invention are disclosed in U.S. Pat. Nos. 4,385,806, 4,436,376, 4,540,243, 4,582,396, and Re. 32,521 and exemplary twisted nematic liquid crystal cells and displays are disclosed in U.S. Pat. Nos. 3,731,986 and 3,881,809.
Another type of liquid crystal light control device is known as a dyed liquid crystal cell. Such a dyed cell usually includes nematic liquid crystal material and a pleochroic dye that absorbs or transmits light according to orientation of the dye molecules. As the dye molecules tend to assume an alignment relative to the alignment of the liquid crystal structure or directors, a solution of liquid crystal material and dye placed between a pair of plates will absorb or transmit light depending on the alignment of the liquid crystal material. Thus, the absorptive characteristics of the liquid crystal device can be controlled as a function of applied electric field.
As is disclosed in several of the above patents, the respective shutters may have one or more operational characteristics (sometimes referred to as modes or states). One example of such an operational characteristic is the shade number; this is the darkness level or value of the shutter when it is in the light blocking mode. Another exemplary operational characteristic is the delay time during which the shutter remains in a dark state after a condition calling for the dark state, such as detection of the bright light occurring during welding, has ceased or detection thereof has terminated or been interrupted. Still another operational characteristic is sensitivity of one or both of the detection circuit or shutter to incident light, for example, to distinguish between ambient conditions and the bright light condition occurring during a welding operation and sensitivity also may refer to shutter response time or to the time required for the circuitry associated with the lens to detect a sharp increase in incident light (e.g., due to striking of the welding arc, etc.) and to switch the lens from the clear state to the dark state. Yet another characteristic, which may be considered an operational characteristic, is the condition of the battery or other power source for the shutter, such as the amount of power remaining, operational time remaining until the power source becomes ineffective, etc. In the past various operational characteristics of such shutters have been adjustable or fixed.
Dynamic operational range or dynamic optical range is the operational range of the lens between the dark state and the clear state, e.g., the difference between the shade numbers of the dark state and the clear state.
An example of a “welding lens with integrated display and method” is disclosed in U.S. Pat. No. 6,067,129. As disclosed therein the current operational characteristics of a shutter can be displayed and can be selectively changed by operating one or more switches. The switches may be flexible membrane switches, microswitches, or another type of switch.
The disclosures of the patents identified herein are specifically incorporated in their entirety by reference.